The present invention relates to a semiconductor fabrication; and, more particularly, to an apparatus for an ultra vacuum chemical vapor deposition and an epitaxial layer growing method therefor, in which a single crystal semiconductor thin film based on a high quality can be prominently grown in a manufacturing nature.
In a complementary metal oxide semiconductor (CMOS) technique, it has been recently further developed a device based on a minimum of feature of 0.13 xcexcm and a memory capacity of 1 giga (G). By such consecutive technique development, it is anticipated to embody the minimum of feature of 0.035 xcexcm and an integration degree of 1010 cmxe2x88x922 in 2012. Further, it is being diversely progressed an endeavor to embody a system-on-chip by improving a function of the CMOS, to thus promote an actual use for a BiCMOS having an addition of SiGe HBT.
However, there is a limitation in reducing the integration degree of the device by using a capability of controlling a reproducibility and a uniformity in a conventional semiconductor manufacturing technique, therefore, it is needed a development for a next-generation semiconductor technique to overcome such limitation. Particularly, in a growth technique of a semiconductor epitaxial layer, most fundamental and decidable method is provided to overcome such limitations.
In the growth technique of the conventional epitaxial layer, there are a gas-source molecular beam epitaxy (GSMBE) method, a rapid thermal chemical vapor deposition (RTCVD) method, a low pressure chemical vapor deposition (LPCVD) method, and a horizontal type ultra high vacuum vapor deposition (UHV-CVD) etc.
The gas source molecular beam epitaxy (hereinafter, referred to as xe2x80x9cGSMBExe2x80x9d) using a gas source has been being used most frequently in a research institute, and this technique provides a growth characteristic of an epitaxial layer prominent in an interfacial abruptness under a pressure of 600xc2x0 C. and 1.4xc3x9710xe2x88x924 Torr. But, the GSMBE is unstable in using the source, causes a ge-segregation of germanium, makes a cost and usage expenses high, and has a low throughput thus its productivity is shortage, therefore there is a limitation that it is difficult to be applied to a producing technique.
The RTCVD of FIG. 1 in a conventional another technique relates to a viscous laminar flow, in other words, is valid to perform a growth under a pressure of 6 Torr, and has a growth function by maintaining the flow with hydrogen gas in a cold-wall reactor 3 having an installment of a single wafer 1 and a cooling plate 2, and matches temperature and changes reaction gas. Thereby, the RTCVD has a growth function. That is, a growth process is simple and its usage is various, but reproducibility important in a growth of the epitaxial layer rapidly performing a temperature control is insufficient therein, and it is not open used owing to a shortcoming of representing a loading efficiency.
Subsequently, as shown in FIG. 2, the LPCVD controls a leak rate as 1 mTorr/min and controls a growth rate as 0.4xcx9c4 nm/min. Since this LPCVD is a low pressure, it is convenient to manufacture or use the device, thus this device has been used most much in order for a polycrystal thin film of silicon or a vapor deposition of an insulation film such as an oxide film or a nitride film. However, it is lack in a function of cutting off oxide or moisture injected from the neighborhood of a chamber 3. In other words, in order to deposit a thin film based on a high purity, it is needed to execute a purge with hydrogen gas for a long time, and an epitaxial layer based on a lower quality is grown in comparison with the technique obtaining the growth in a high-vacuum chamber. Herewith, an unexplained reference number xe2x80x982xe2x80x99 indicates the cooling plate.
The horizontal type UHV-CVD shown in FIG. 3 is for an apparatus and method for growing a single-crystal silicon epitaxy by several sheets in an isothermal chamber 4 of a how wall, and has growth temperature below 800xc2x0 C., and restricts a growth rate by non-plain power. By the silicon gas within the isothermal chamber, a uniform growth of an epitaxial layer is gained on a wafer 1 of several sheets, and an ultra-high vacuum of 10xe2x88x9210 torr is supported before a start of the growth, and the silicon epitaxial layer is defined as a very keen region at the moment when the silicon epitaxial layer grows. Therefore, the epitaxial layer under 500 defects per a unit area cm2 can grow. Such horizontal type ultra-high vacuum growing device is simple in its manufacture since the wafer can be transferred horizontally, but there is a serious shortcoming of accumulating the vapor deposition in the growth chamber and of a systematic footprint.
It is anticipated that the Moore laws will become relieved in an aspect of incline from a start point of about 2010 year provided under about 100 nm, since an added value of the integration reaches some limitation. Also, according that a structure and a function not used at the past are strengthened in the silicon semiconductor, the integration is gained in a radio frequency (RF) functional device or an optical functional device, to thus obtain the system-on-chip and remarkably heighten a cost and a performance of a semiconductor chip. In its concerning problems, a management for electric power through a low power operation and a curtailment for a manufacturing cost of the semiconductor etc. are proposed, and it will be mainly provided a research to overcome such technical difficulties as a development of a process technique through a development start of a device structure under 100 nm in the minimum of feature from around 2003 year, a new physical field for a quantization effect and an uncertain current flow, an excessive electricity consumption, a complication of a design and a tunneling.
For instances, in a modulation FET (MODFET), a characteristic of a high-speed operation is improved by generally heightening a movement extent of a transferor, leakage current is small, and a nonlinear operation characteristic caused in a single channel is improved, therefore there were much research. However, in a case of SiGe-MODFET, there still is a serious problem in a commercial use thereof.
An application of SiGe semiconductor was initially proposed by Herbert Kroemer in 1957, and SiGe low-temperature growth applicable to a device was initially proposed by Meyerson of IBM in 1981. But, an actually operating SiGe HBT was published by Meyerson in 1987 by completely satisfying a characteristic of the device through a growth of the epitaxial layer. According to such technical advance, a research for the SiGe was rapidly increased. SiGe-HBT ft=75 GHz (IBM) is published in 1990, SiGe BICMOS in 1992, and SiGe-HBT ft=100 GHz in 1994, through a renewal of a record in order. Also the IBM announced a commercial use of SiGe HBT on 8-inch wafers in 1994. In 1998, not only the IBM but also several companies such as TEMIC, SGS Thompson, and Maxim etc. had initially provided an LNA, a Mixer, a power amplifier, and a VCO etc.
The most important one to realize the device of SiGe and improve it with a prominent characteristic was depended upon a technical achievement in the SiGe epitaxial layer growth. A grid discordance between Si and Ge is severe as 4.2%, thus there is a limitation in its usage, since a threshold thickness is 80xcx9c100 nm when XGe is 8xcx9c12% and the threshold thickness is 40xcx9c50 nm when XGe is 16xcx9c24%. Further, when a growth condition is not appropriate, a thermal shock is provided, or an impurity substance exists on the surface of a wafer, a large amount of defect is caused easily. In a merit point in using the SiGe, the SiGe layer receives a pressure stress to degenerate a band and thus heighten a movement degree of a transferor, it is applicable to a light receiving element by controlling energy gap energy Eg by 0.66xcx9c1.12 eV, and a band gap discordance mainly exists on a valence band in an n-p-n structure of a bipolar element to thereby make a movement of electron easy and heighten an efficiency by reducing a hole injected from a base to an emitter, etc.
In checking the growth technique of the SiGe epitaxy, a composition of Ge should uniformly grow within 5%, a consistency of C and O as impurity substances injected from an interfacial neighborhood should be small, and there should exist a control capability of a doping consistency keen enough to be several numbers of atomic layers. Herewith, also, a performance similar to a general process technique for a growth provided through a disposition of several sheets should be provided, a thermal stableness should be ensured without a problem such as a relaxation of stress or a defect occurrence of a thin film caused on the neighborhood of 600xc2x0 C., and a problem such as leak current between a collector and a base should be eliminated by an epitaxy based on a low defect, namely, a high yield and low expenses. Furthermore, properties of matter based on a high quality should be maintained even after a furnace anneal of 850xc2x0 C. or a rapid thermal anneal of 900xcx9c1000xc2x0 C.
A function of a low temperature growth is much required, which is why the growth should be performed below 650xc2x0 C. because of problems such as a interfacial diffusion of SiGe/Si and a diffusion of B, and a defect occurrence caused by a stress relaxation of a metastable SiGe layer should be prevented. As problems in the growth of low temperature, a crystal defect becomes contained because a surface diffusion of Si is not sufficient, or an in-situ cleaning of a natural oxide film is inefficient, or a growth rate is low, or n-type and p-type doping based on a high consistency are difficult in the in-situ, or a guarantee for a reliability and a stableness for a long period is difficult.
A growth apparatus requiring a growth of a high vacuum in order to settle the above-mentioned restriction conditions is controlled by a molecular flow below 10xe2x88x923 torr pressure, controls a vapor reaction, and is valid to get a proper combination with a growth provided by a surface reaction control of the low temperature. Especially, an ultra-vacuum growth provides a growth of an epitaxial layer based on a high quality in the low temperature, and also has a small loading effect, and minimizes an injection of defect/impurity, and is also very profitable to a selective epitaxy growth (SEG).
In such high vacuum growth, a growth chamber should be under 10 ppb in moisture and oxide content, and in order to predict a consistency of impurity as oxide injected according to an epitaxy growth condition, in a case of the growth condition such as roughly pressure P=10 Torr, M=32 amu, and temperature T=300 K, a quantity of reactive gas reaching a unit surface of the wafer is as follows:
      Z    A    =      2.63    xc3x97          10      22        ⁢          xe2x80x83        ⁢          P              MT              ⁢          xe2x80x83        ⁢          (                        cm                      -            2                          ⁢                  s                      -            1                              )      
It can be noted that its value becomes ZA=3.6xc3x971021 cmxe2x88x922 sxe2x88x921. Also, even though the growth rate is 1 nm/s and a sticking coefficient of impurity gas atom is very low as 0.01, in case that a grown pressure is 10xe2x88x923 Torr and 10 Torr and there exists the impurity gas of 100 ppb, the amount of the impurity injected in the epitaxy is 4xc3x971015 cmxe2x88x923 and 5xc3x971018 cmxe2x88x923, there is much difference therebetween. Such injection of the impurity is also increased by 10 times under 100 ppb.
In the chemical vapor deposition apparatus it can occur very easily the impurity gas of 1000 ppb according that how the growth chamber is designed and used.
In the growth of the SiGe and Si epitaxy, the low-temperature growth is being highlighted as technique useful in a manufacture of a device having a surface rapid and small in size. Particularly, the high-consistency phosphorus doping n+-silicon epitaxy based on the low temperature is definitely needed to manufacture an Si/SiGe heterostructure device such as MODFET(Modulation-Doped FET), MOSFET (Metal-Oxide-Semiconductor FET), and HBT (Heterojunction Bipolar Transistor).
In executing the chemical vapor deposition (CVD), it has been mainly used phosphine or arsine as n-type dopant.
The low-temperature growth of the high-consistency n+-silicon layer is being actively researched to apply it to the SiGe heterostructure or a small-sized device of a nanometer unit. Especially, it is known that an impurity diffusion, an intermixing of Si/Si1xe2x88x92xGex interface and a stress relaxation etc. occur over a constant temperature, to have a harmful influence on a performance of the device. Meantime, a systematic research for the low temperature growth of silicon related to the n-type dopant injection is scarcely executed. To execute the low temperature growth of the n-type silicon epitaxy, it is essentially needed a technique for removing the natural oxide film existing on the substrate in rather low temperature. At present, a real time (in situ) hydrogen thermal anneal for removing the natural oxide film must be performed for several minutes under temperature of 900xc2x0 C. in order to remove the natural oxide film, by the time, in manufacturing the device, it can not be executed a high-temperature hydrogen thermal anneal process to eliminate the natural oxide material after performing a vapor deposition for the SiGe layer. Therefore, it has been regarded, as an alternative method, a method of etching the surface within reactive gas such as HF, HCl and methanol or their mixture etc. However, the reactive gas causes an unequal pin hole on the surface thereof or corrodes an oxide film mast layer. Thus, it is required a technique for forming the silicon epitaxial layer based on a good quality without a high-temperature thermal anneal process.
Therefore, it is an object of the present invention to provide an apparatus for a perpendicular-type ultra vacuum chemical vapor deposition, in which a thin film based on a high quality can grow under low pressure and low temperature of 10xe2x88x923 Torr and 500xc2x0 C. by disposing wafers by 50 pieces or over at one time, thereby obtaining a sufficient throughput by the equipment for a production.
Another object of the present invention is to provide an apparatus for a perpendicular-type ultra vacuum chemical vapor deposition appropriate to that a growth to an atomic unit under low temperature is gained, impurity based on a high consistency is doped in a two dimension, or a 2 DEG quantization effect device is manufactured, by reducing contents of oxygen or carbon to a basic vacuum of 1xc3x9710xe2x88x929 Torr.
A still another object of the present invention is to provided an apparatus for a perpendicular-type ultra vacuum chemical vapor deposition, in which a defect extent can be lowered and a width of a doping consistency can be controlled so as to become narrow and keen on a wafer having a pattern by controlling an exact thickness, composition and consistency.
A further object of the present invention is to provide an apparatus for a perpendicular-type ultra vacuum chemical vapor deposition, which is capable of cutting off a flow of current provided by an inversion of a silicon cap layer Si-Cap in a general SiGe-MODFET, preventing a flow of leak current caused by a precipitation of Ge generated in forming an oxide film, and preventing a diffusion in high temperature when performing an epitaxial layer growth or a manufacture process.
To achieve these and other advantages, and in accordance with the purpose of the present invention, an apparatus for a perpendicular-type ultra vacuum chemical vapor deposition comprises a growth chamber having a quartz tube of a heterostructure for maintaining a uniformity of an epitaxy growth under a high vacuum and minimizing a thermal transfer from a wafer; a wafer transferring chamber connected to a lower side of the growth chamber, the wafer transferring chamber having a perpendicular transfer device for vertically transferring the wafer on which the epitaxy grows; a buffer chamber equipped in a lower side of the wafer transferring chamber, for preventing a stress to a transfer gear caused by a pressure difference with the wafer transferring chamber in vertically transferring the wafer; and a loadlock chamber connected to one side of the wafer transferring chamber, for reducing a pollution from the outside in a growth of the epitaxy, horizontally transferring the wafer completed in the growth of the epitaxy, and discharging it to the outside: wherein the quartz tube of the heterostructure includes an inner quartz tube having a support flange in a lower part thereof, the inner quartz tube being opened in a lower end part thereof; an outer quartz tube supported to the support flange of the inner quartz tube with a constant interval from the inner quartz tube, the outer quartz tube having a support flange in a lower part thereof and being opened in a lower end part thereof; a cooling water tube equipped in an outer side of the support flange of the outer quartz tube, for preventing a hear transfer transferred to the outer quartz tube; a thermocouple equipped along one side inner circumference face of the inner quartz tube and a gas injecting part equipped along another side inner circumference face of the inner quartz tube; and a vacuum port for providing vacuum by opening one side face of one side support flange of the outer quartz tube, the thermocouple and the gas injecting part being connected to the support flange of the inner quartz tube with a lower end part thereof, and a center part of the support flange of the inner quartz tube having a formation of an opening aperture provided as an inlet and an outlet for loading and unloading the wafer: and wherein the perpendicular transfer device within the wafer transferring chamber includes an upper flange opened in a center thereof, for separating the growth chamber and the wafer transferring chamber during a growth of the epitaxy; a wafer carrier accepting numerous wafers and supported thereby; a quartz bottom plate for supporting the wafer carrier; a wafer transfer die connected to the quartz bottom plate, for supporting the wafer carrier on which the wafers are accumulated, and vertically moving it; a lower flange stuck to the buffer chamber and opened in a center thereof; a primary convey die having a primary transfer gear and an outer bellows connected between one side of the upper flange and the buffer chamber, the outer bellows for upwards moving the upper flange; and a secondary convey die which has a secondary transfer gear connected to the wafer transfer die and has an inner bellows connected between the upper flange and the secondary transfer gear so as to position the wafer carrier vertically transferred by the primary convey die at a uniform temperature region of the growth chamber, the inner bellows being moved upwards by a rotation of the secondary transfer gear.